Effect of pH and salt concentration on the solubility and density of egg yolk and plasma egg yolk

This work aimed to evaluate the solubility and density of egg yolk and plasma egg yolk in three types of salts (NaCl, Na₂SO₄ and (NH₄)₂SO₄) at different pH values (3.0, 4.03, 6.5, 8.7 and 10.0) and salt concentrations (0.05, 0.1, 0.2, 0.3 and 0.5 mol/l). Solubility data of both egg products showed a distinct behaviour for each type of salt. A 4th-order polynomial model fitted the solubility data with R² values higher than 0.83. It was observed the increase of the density as the salt concentration increase. The model used for density data correlation shown R² values higher than 0.94.     

蛋清发酵饮料的研究

以蛋清为主要原料 ,加入牛乳、糖类 ,进行乳酸发酵 ,确定了蛋清液的杀菌条件 ;通过正交实验和品评实验 ,确定了发酵时混合菌的配比、接种量、牛乳的添加量、发酵的最佳时间及温度 ;探讨了发酵品的调制 ,提出了生产的最佳工艺流程 ;为防止乳清分离及凝絮沉淀 ,用黄原胶作稳定剂 ,并取得满意的效果     

鸡蛋保鲜技术研究进展

鸡蛋营养丰富,深受广大消费者的喜爱,但由于受产蛋淡旺季、疫病等因素的影响,鸡蛋销售价格波动较大,因此,鸡蛋保鲜技术成为研究的热点。本文系统介绍了应用前景较大的鸡蛋保鲜技术,并阐述了鸡蛋保鲜技术的发展趋势。     

氯仿-甲醇法和酸水解法测定禽蛋中脂肪的方法比较

目的 对比富含磷脂等结合态脂肪的蛋制品中脂肪含量测定的方法,弥补目前国标中规定的酸水解检测方法无法准确地测定富含磷脂等结合态脂肪样品的不足。方法 采用氯仿－甲醇提取法对比国标中规定的蛋制品脂肪测定方法-酸水解法,测定蛋制品中的脂肪含量, 考察了两种方法测定不同蛋制品的提取结果、提取时间、精密度和重复性。结果 采用氯仿－甲醇法对比酸水解法提取蛋制品中的脂肪含量,结果表明,氯仿-甲醇提取法可以有效的提取蛋制品的磷脂等结合态脂肪,对蛋制品脂肪的测定具有较高的精密度和较好的重复性,相对标准偏差在0.91%-1.62%之间,且测定周期短,测定次数少。结论 氯仿－甲醇法弥补了酸水解法水解磷脂的不足且测定快速、准确,适合测定蛋制品中的脂肪含量。     

固相萃取-高效液相色谱法测定禽蛋中斑蝥黄和叶黄素

目的对目前尚未列入监控的禽蛋中类胡萝卜素着色剂(斑蝥黄和叶黄素)建立高效液相色谱检测方法。通过优化测定条件及前处理方法,有效排除蛋黄中脂肪、蛋白质等带来的干扰。方法样品经正己烷超声提取,过中性氧化铝柱净化,采用C_(30)色谱柱(4. 6 mm×250 mm,5μm)分离,用含0. 1%二丁基羟基甲苯的乙腈-甲基叔丁基醚(8∶2,V/V)和水溶液梯度洗脱,高效液相色谱法测定,外标法定量。结果在优化后色谱条件下,斑蝥黄和叶黄素在0. 20～10. 0 mg/L浓度范围内,线性关系良好,相关系数(r)≥0. 999 3,方法检出限分别为0. 02和0. 08 mg/kg,回收率为89. 3%～102%,相对标准偏差(RSD)为2. 2%～4. 9%。结论该方法快速、准确、灵敏,适用于禽蛋中斑蝥黄和叶黄素的同时测定。     

Continuous centrifugal fractionation of egg yolk granules and plasma constituents influenced by process conditions and product characteristics

The egg yolk main fractions, granules and plasma, show considerable different emulsifying properties. In order to use this potential, the present study investigates the influence of variable process conditions on the continuous centrifugal separation process of liquid egg yolk. It is shown that the granule fraction represents no homogeneous component, but consists of three different subfractions with different size, density and structure. It was confirmed by SDS–PAGE that each granule subfraction incorporated different amounts of LDL. The inhomogeneity leads to a subfraction depending sedimentation behaviour of the whole granule-fraction in egg yolk which could be clearly classified. Based on these findings, the impact of variable rheological properties on the sedimentation behaviour of polydisperse suspensions with high particle concentrations is discussed. However, fluid temperatures of 50 °C, a dry matter reduction below 29% prior to the centrifugal fractionation and g-forces up to 10,000g resulted in excellent separation efficiencies of the granule-fraction.     

Influence of glycerol and water activity on the properties of compressed egg white-based bioplastics

In this paper, the effects of glycerol (35%, 40% and 45%) and water activity (0.34 and 0.48) on the physical, mechanical and morphological properties of compressed egg white-based bioplastics are investigated. Lighter, more reddish and less yellowish sheets with a decreased thickness and second-order transition temperature, improved mechanical properties (increased flexibility and decreased rigidity and stiffness) and constant moisture content can be obtained by increasing water activity. Increasing the GLY content results in the same type of changes but to a lesser extent and increased moisture content. Increasing both, water activity and GLY, leads to a more pronounced effect for some properties. This study demonstrates that compressed egg white-based bioplastics with desired properties can be obtained by adjusting water activity and GLY content during their synthesis.